SU1388437A1 - Slag-formingg mixture - Google Patents

Abstract

The invention relates to ferrous metal metalwork, namely to mixtures. For obtaining slags used in smelting and processing of iron-carbon melts. The aim of the invention is to improve the mechanical properties of cast iron. The slag-forming mixture contains, by weight,%: metal-silicon waste production of synthetic cast iron 60-80; known to 10-30 and fluorspar the rest. The use of a slag-forming mixture makes it possible to increase the tensile strength and yield strength by 20–25%, the relative narrowing by 10% with an increase in hardness by 10–15%, table 3.

Description

CO 00 00 4:

with

 one

The invention relates to the metallurgy of ferrous metals, namely to mixture compositions for the production of slags used in the smelting and processing of iron-carbon melts.

The purpose of the invention is to improve the mechanical properties of cast iron.

The proposed slag-forming mixture contains metal-silicon waste, the production of synthetic iron, limestone and fluorspar in the following ratio of components, wt.%: Metal-siliceous

waste production

synthetic cast iron 60-80 Known to 10-30

Fluorspar Remaining Positive effect from the introduction of the composition of the mixture of metal-silicon waste from the production of synthetic cast iron, containing, in wt.%: 15-20; Sic 37; SiO 1-3; From ,, „15-26; the rest of the iron allows to expand the metallurgical potential of smelting, without using expensive ferroalloys for this purpose. Metal-silicon waste is formed when synthetic iron is injected due to the difference in the specific gravity of lumpy ferrous sr 5 when it is added to the ditch, and liquid iron. In this case, the low specific surface of pieces of ferrosilicon leads to an elongation of the process of its dissolution and reduces the efficiency of its use, despite the use of such complex mechanical means as agitators, gutter walls, etc.

When ferrosilicon is fed to a ditch in a cast iron ladle, a refractory crust is formed on the surface of the iron melt, consisting of entangled iron, undissolved ferrosilicon and graphite.

After discharging synthetic iron from the bucket, the bucket is cleaned of the remaining crust in it, which is not used later and is sent to the dump. This crust, which is a metal-silt waste, is proposed to be used in the composition of the raw mix.

The preparation of the metal-silicon additive for use as a component in the mixture consists in crushing the crusts to a fraction of less than 100 mm and cleaning it from the graphite pyule by air separation or another method.

372

Then, the metal-silicon waste is mixed with limestone and fluorspar V, the raw mix is stored in bunkers specially designated for this purpose.

The use of a metal-silicon waste in the mixture increases the metallurgical activity of the slag obtained from it due to the presence of silicon, carbon, and their compounds in the form of silicon carbide in the waste. The positive effect is achieved by the fact that the chemical composition of metal-silicon waste ensures an active course of iron reduction reactions from oxides, since the thermodynamic activity of carbon and silicon, which is part of the waste both in pure form and in the form of silicon carbide, is high relative to iron oxides If the thermodynamic activity of silicon to 1400 ° C exceeds the activity of carbon, then in the temperature range above 1400 ° C, the activity of carbon is higher. silicon activity. The combined use of carbon and silicon makes it possible to compensate for their shortcomings as reducing agents under continuously changing conditions.

The reduction of iron in this case proceeds according to the following reactions:

SiC + + SiO + CO

C + FeO Fe + CO

Si -1 2 FeO 2 Fe +, SiO.

As can be seen from the reactions, the products of the reduction of iron oxide are Fe, SiOj and CO, as a result of which a donkey is formed with an increased concentration of S i02. This leads to an increase in the viscosity of the slag and the deterioration of the kinetics of the reduction processes. In order to compensate for the effect of the formation of silica on viscosity and on refining of the slag capacity, limestone and fluorspar are introduced into the mixture.

Calcium oxide reduces the viscosity of the slag and, as a stronger compound, destroys the filament present in the slag, increases the activity of ferrous oxide in the slag and increases the degree of its reduction:

Red504 + 2SaO

Ca2Si04 + 2FeO.

The content of limestone in a mixture of less than 10% does not ensure the complete slagging of silica, whereas an excess of more than 30% is impractical, since its content to this limit ensures complete slagging of the silica.

Fluorspar contributes to the creation of liquid slag. In addition, calcium fluoride, together with calcium oxide, provides slag with refining properties that reduce the content of sulfur in the smelted alloy.

A decrease in the content of the metal-silicon waste in the mixture below 60% of the limit does not provide adequate modification, deoxidation and insufficiently restores iron from oxides; .

B tab. 1 shows the data on the properties of the slag obtained from the proposed mixture, reflecting the degree of influence of various mixture compositions on them.

As can be seen from the table. 1, the slag has a sufficiently high melting point and viscosity, which ensures high temperatures during the electroslag process and contributes to a high degree of overheating of the melt, its refinement and modification.

In tab. Table 2 lists the compositions of the tested slag-forming mixtures for smelting and treating gray iron (mixtures 1–3 are known mixtures).

Test slag smelted from the known and proposed mixtures, produced as follows.

The pre-mixed slag-forming mixture was remelted in an electric arc furnace, after which the furnace was transferred to an arc-free electric slag mode, reducing the voltage, and the metal charge of the following design composition,%, was taken into the furnace: C 3.2-3 , 3; Si 1.9-2.0; Mp 0.7-0.8; .S 0.11-0.12; P to 0.14. Melting was carried out in a semi-industrial single-phase electroslag furnace with a non-consumable graphite electrode. The furnace was powered by a TPO 250/40 PC oven transformer. Portia

The mixtures were melted and the melt was processed for 15 minutes, after reaching 1500 ° C. The temperature of the slag was maintained at around 1,650. + 20 ° С. The effect of the treatment obtained by the slag on the change in the chemical composition and mechanical properties of the smelted iron was studied.

The chemical composition and mechanical properties of the pig iron, made using the slag prepared from the mixture offered by the slag, are compared with the known mixture used for this purpose (the experiments were carried out under the same conditions) are given in Table. 3

As can be seen from the table. 3, cast iron smelted and treated with slag obtained from the proposed mixture has higher mechanical properties compared to treatment with a known mixture, which is explained by significant desulfurization, exceeding 90%, as well as the modifying effect of slag containing high-alumina melts containing Si in the form of complex components. The modified effect is also confirmed by the fact that the chill of the obtained iron is significantly less.

From tab. 3 also shows that the pig iron treated with the proposed mixture has a higher content of C, Si and Mn. This is due to the positive effect of the metal waste components (silicon, carbon, silicon carbide). Silicon carbide, having a high melting point and close to slag density (3.2 g / cm), is in the slag layer in a heterogeneous state, retaining a high reactivity. In addition, silicon carbide is characterized by a high resistance to oxidizing atmosphere, which reduces its oxidation rate and makes it an effective diffusion deoxidizing agent. The oxidizing ability of the slag obtained from the proposed mixture is also confirmed by the color of the slag, which was greenish-olive.

Thus, the used slag-forming mixture makes it possible to smelt modified cast iron with improved properties without using this expensive ferroalloy for this purpose. Formula - from about brit yeni

Slag-forming mixture including fluorspar and carbonaceous

material, characterized in that, in order to improve the mechanical properties of cast iron, it additionally contains limestone, and as a carbon-containing material

in the following ratio tov, wt.%:

Synthetic metal production

Table 3

Note. The numerator is the value before processing, the denominator is after processing

Claims (3)

Claim Slag-forming mixture, including fluorspar and carbon-containing 5 1388437 material, characterized in that, in order to increase the mechanical properties of cast iron, it additionally contains limestone, and as a carbon-containing material contains silicon-containing waste products of synthetic cast iron production in the following ratio of components tov, wt.%: Silicon-silicon $ production waste wa synthetic cast iron 60-80 Limestone 10-30 Fluorspar Rest Table 1 . Soi tav Content, wt.%, Components Silicon-silicon waste from the production of synthetic iron Known Fluorspar Properties obtained Melting ^point? FROM Viscosity at 1350 ° C 1 55 35 Rest 1220 0.60 2 60 thirty 1230 0.60 3 70 20 _eleven_ 1246 0.62 4 80 10 1260 0.64 5 85 5 1264 0.65 T a b l and 2 Vari- Content components mixtures, May.% mixtures Silicon-silicon waste of synthetic iron production Limestone Shungite 75 - ⁸⁵ - 95 35 thirty - 20 Fluorspar The rest is 11 1388437 8 Continuation of the table. 2 The content of the components of the mixture, wt.% ant —— b mixtures Silicon-silicon waste of synthetic iron production Limestone Shungite Fluorspar 7 80 10 Table 3 Charge option The chemical composition of cast iron, May. 2 Mechanical properties FROM Si ' Mp S R Limit Limit Relative-. Tver durable- fluid body Dost Ti St., narrowing HB kgf / nm ^! kg / mm ¹ f mm 1x23.27 1.8 3 _X 3 _229 3.0 ~ 207 _ ³ 2.3_ 1.96 _ο _Λ ΖΖ. 0.11 0.12 24.4 48.1 W _x 2_ 217 Z 3.25 1.82 o77z 0.08 0.11 21,2 40.8 3.0 207 s 3 _x 3 lt2Z 0.78 0 _x 11 ΛΔί- 25χ1 Huh? .2 40,2 - 3χ2_ 229 3.24 ',8 0.75 0.09 0.14 20.6 2.9 217 4 3 ^ 28 1.90 - ° x22- 0.11 _2χ12_ -11x2- -1x2- 3.0 217 .3.34. 1.94 0.78 0.06 0.12 26.2 52.1 241 5 3.26 121 0.71 ° x11_ 2 ° χ8 40.1 3 ° 207 3.32 1.96 0.74 0.06 0.12 26.1 51.9 3,1 217 6 3.26 -1x21. 0.73 Oj.ll 0 _χ 12 _Z2bl_ 42.0 3,1 217 229 3.31 1.99 0.77 0.05 0.12 30.5 49.1 3.3 at  A2__ 1.92 0.74 0.11 0.13 22.4 29 3 * 43.1 3.0 297 241 3.36 2.01 0.77 0,03 0.12 52.6 3.2 3.3 1.93 0.75 0.11 0.12 21.0 41.6 S _x 0 207 8 3.36 2.03 0.77 0,03 0.12 2b, 8 .¾ 53 ~ 2 ^ T Note. Numerator - values before processing, denominator - after processing